We’re not in 1990 anymore, Toto, thanks to forces driving voters to more uniformly back a single party. The Democratic and Republican parties have grown farther apart ideologically, and voters are increasingly likely to say that there are sizable differences between the parties. At the same time, voters’ political views have also become more polarized, with more Democrats becoming consistently liberal and more Republicans becoming more consistently conservative. And because of negative partisanship, voters are now more inclined to dislike the other party out of hand, making them less likely to consider voting for a candidate from the opposite party under any condition. These developments have left the country with fewer swing voters than ever; despite the large number of Americans who claim to be independent, most in fact prefer one side. More broadly, politics are more nationalized, which has reduced regional variation in elections for Senate or governor, making it less likely that ru...